Until now, toll concepts have been known in which in each case a toll operator is assigned a single toll registration region and said toll operator bills the tolls in accordance with the traffic volume entering this area, directly with the toll operator.
If a plurality of operators of toll systems accept each other's vehicles or vehicle devices in order to bill the toll in their own respective region, the demands placed on the means for protecting the entire system against fraud and the demands placed on all those involved become complex.
In the field of banking, such a complex structure and demands have been dealt with in Europe by selecting a key management system which is hierarchical. The European Central Bank has a main key whose public part is known to all, and each hierarchical layer below it has its key confirmed by the European Central Bank and this occurs correspondingly in the layers below that. As a result any bank can check the public key of any other bank if this bank firstly trusts only the key of its hierarchical mother and then the confirmation chain runs up the hierarchy and down again to the corresponding bank. A disadvantage of this solution is that there has to be a clearly defined hierarchy, which is not possible in the field of tolls. Such a central key management function is not acceptable owing to the powerfulness of such a device.